Process for producing thermoplastic elastomer composition, and process for producing foamed thermoplastic elastomer composition

Abstract

A process for producing a thermoplastic elastomer composition comprising the steps of (1) heating dynamically (A) a defined ethylene-α-olefin random copolymer rubber, (B) a propylene homopolymer, or a defined copolymer of propylene with ethylene and/or an α-olefin, (C) a mineral oil softener, and (D) a crosslinking agent, and (2) melt-kneading the resultant product with a defined polypropylene resin (E); and a process for producing a foamed thermoplastic elastomer composition comprising the further step of melt-kneading said thermoplastic elastomer composition with (F) a foaming agent.

1. A process for producing a foamed thermoplastic elastomer composition, which comprises the steps of:
 (1) heating dynamically at least the following components (A), (B), (C) and (D), thereby producing an intermediate product: 
 (A) 100 parts by weight of an ethylene-α-olefin random copolymer rubber, which contains at least an ethylene unit and an α-olefin unit having 3 to 10 carbon atoms, and has hardness-A defined in JIS K-6253 of 98 or smaller; 
 (B) 5 to 130 parts by weight of a propylene homopolymer, or a random or block copolymer of propylene with ethylene and/or an α-olefin having 4 to 10 carbon atoms, said homopolymer and said copolymer containing 50 to 100% by weight of a propylene unit, wherein the total amount of all units contained therein is 100% by weight; 
 (C) 5 to 150 parts by weight of a mineral oil softener; and 
 (D) 0.01 to 20 parts by weight of a crosslinking agent; 
 (2) melt-kneading at least said intermediate product with 1 to 50 parts by weight of a polypropylene resin (E), which contains 0.05 to 25% by weight of the following first propylene polymer component (E1) and 75 to 99.95% by weight of the following second propylene polymer component (E2), and has an intrinsic viscosity of 0.5 to 4 dl/g and a molecular weight distribution of 1 to 10, wherein the total amount of the first propylene polymer component (E1) and the second propylene polymer component (E2) is 100% by weight: 
 (E1) a first propylene polymer component which has an intrinsic viscosity of 7 to 10 dl/g; and 
 (E2) a second propylene polymer component which has an intrinsic viscosity of 0.5 to 4 dl/g; 
 wherein each of the component (E1) and the component (E2) is a homopolymer of propylene; 
 
       thereby producing a thermoplastic elastomer composition; and
 (3) melt-kneading at least said thermoplastic elastomer composition with (F) 0.5 to 20 parts by weight of a foaming agent. 
 
     
     
       2. The process for producing a thermoplastic elastomer composition according to  claim 1 , wherein the component (A) is an ethylene-propylene copolymer rubber or an ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber. 
     
     
       3. The process for producing a thermoplastic elastomer composition according to  claim 1 , wherein the component (B) is a homopolymer of propylene, an ethylene-propylene copolymer or a propylene-1-butene copolymer. 
     
     
       4. The process for producing a thermoplastic elastomer composition according to  claim 1 , wherein the component (D) is an organic peroxide. 
     
     
       5. The process for producing a thermoplastic elastomer composition according to  claim 1 , wherein the component (E) is produced according to a process comprising the steps of (i) producing the component (E1), and (ii) producing the component (E2) in the presence of the component (E1). 
     
     
       6. The process for producing a thermoplastic elastomer composition according to  claim 1 , wherein the component (C) is paraffinic mineral oil.